Instead, the bank's newly installed CEO, Michael Corbat, will more likely preside over a cultural shift that includes radically slimming down the bank's emphasis on trading.

Citigroup cannot simply separate commercial banking from investment banking because both units serve many of the same clients.

And it's carved out a particularly sweet spot with corporate clients, where Citi's investment bankers work directly with commercial bankers to provide a host of offerings, including loans, derivative products and M&A advisory services.

"I don't think a separation of the investment bank from the commercial bank is feasible today," said an investment banker and former senior executive at Citi who works on M&A activity on behalf of major banks, but declined to be identified. "It's impractical, if not impossible. How do you split up a business when there's so much overlap?" he added.

Even simply selling off Citigroup's credit card unit would be challenging, since that serves its consumer base and allows Citi to collect additional fees from its banking customers.

Some international divisions could in theory be spun off or sold, but that would force Citi to lose some of its " international jewels," the banker said. Citigroup's subsidiary in Mexico, Banemex, is one of the country's largest consumer banks, but selling that would likely hurt Citi's options in Mexico over the long-term.

The biggest bullseye? Trading.

Trading had been a major focus under Pandit, who spent more than two decades in Morgan Stanley's trading units before co-founding Old Lane, a hedge fund he sold to Citi for $800 million in 2007.

While Pandit has been forced to slim down Citigroup over the last several years by selling off its wealth brokerage business Smith Barney and life insurance firm Primerica, the bank has only minimally scaled back its stock, bond and derivatives trading activity.

Several current and former employees expect Corbat's knife to hit there. Michael O'Neill, the chairman of Citigroup's board, is seen as a back-to-basics banker and Corbat is expected to follow his lead.

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Corbat told investors on a conference call Tuesday that he was going to take time to review Citi's businesses and there would be some changes coming. But he emphasized that the bank's overall business model was the right one. The bank declined to comment further.

Corbat, a 29-year veteran of Citigroup, initially joined Salomon Smith Barney, which became part of Citigroup during former CEO Sandy Weill's roll-up of an array of financial institutions. Yet many within the bank see him as a more traditional commercial banker, more focused on serving clients than finding creative ways to generate investment banking fees. In the early part of this decade, Corbat spent several years running Citi's global commercial bank.

The new CEO is also well-versed in unwinding assets. He ran Citi Holdings, the unit housing the bank's "bad" legacy assets from the financial crisis, and worked on the sale of over $500 billion of troubled holdings.